Auto merge of #134353 - oli-obk:safe-target-feature-unsafe-by-default, r=wesleywiser

Treat safe target_feature functions as unsafe by default [less invasive variant]

This unblocks
* #134090

As I stated in https://github.com/rust-lang/rust/pull/134090#issuecomment-2541332415 I think the previous impl was too easy to get wrong, as by default it treated safe target feature functions as safe and had to add additional checks for when they weren't. Now the logic is inverted. By default they are unsafe and you have to explicitly handle safe target feature functions.

This is the less (imo) invasive variant of #134317, as it doesn't require changing the Safety enum, so it only affects FnDefs and nothing else, as it should.

39 files changed, 319 insertions, 120 deletions

diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 758f1dc1c35..266e77c0e02 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -188,7 +188,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
     ) -> hir::FnSig<'hir> {
         let header = if let Some(local_sig_id) = sig_id.as_local() {
             match self.resolver.delegation_fn_sigs.get(&local_sig_id) {
-                Some(sig) => self.lower_fn_header(sig.header, hir::Safety::Safe),
+                Some(sig) => self.lower_fn_header(
+                    sig.header,
+                    // HACK: we override the default safety instead of generating attributes from the ether.
+                    // We are not forwarding the attributes, as the delegation fn sigs are collected on the ast,
+                    // and here we need the hir attributes.
+                    if sig.target_feature { hir::Safety::Unsafe } else { hir::Safety::Safe },
+                    &[],
+                ),
                 None => self.generate_header_error(),
             }
         } else {
@@ -198,7 +205,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 Asyncness::No => hir::IsAsync::NotAsync,
             };
             hir::FnHeader {
-                safety: sig.safety,
+                safety: if self.tcx.codegen_fn_attrs(sig_id).safe_target_features {
+                    hir::HeaderSafety::SafeTargetFeatures
+                } else {
+                    hir::HeaderSafety::Normal(sig.safety)
+                },
                 constness: self.tcx.constness(sig_id),
                 asyncness,
                 abi: sig.abi,
@@ -384,7 +395,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     fn generate_header_error(&self) -> hir::FnHeader {
         hir::FnHeader {
-            safety: hir::Safety::Safe,
+            safety: hir::Safety::Safe.into(),
             constness: hir::Constness::NotConst,
             asyncness: hir::IsAsync::NotAsync,
             abi: abi::Abi::Rust,
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 6fce9116938..61d7da429f8 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -231,7 +231,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     });
                     let sig = hir::FnSig {
                         decl,
-                        header: this.lower_fn_header(*header, hir::Safety::Safe),
+                        header: this.lower_fn_header(*header, hir::Safety::Safe, attrs),
                         span: this.lower_span(*fn_sig_span),
                     };
                     hir::ItemKind::Fn { sig, generics, body: body_id, has_body: body.is_some() }
@@ -610,7 +610,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
         let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         let owner_id = hir_id.expect_owner();
-        self.lower_attrs(hir_id, &i.attrs);
+        let attrs = self.lower_attrs(hir_id, &i.attrs);
         let item = hir::ForeignItem {
             owner_id,
             ident: self.lower_ident(i.ident),
@@ -634,7 +634,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         });
 
                     // Unmarked safety in unsafe block defaults to unsafe.
-                    let header = self.lower_fn_header(sig.header, hir::Safety::Unsafe);
+                    let header = self.lower_fn_header(sig.header, hir::Safety::Unsafe, attrs);
 
                     hir::ForeignItemKind::Fn(
                         hir::FnSig { header, decl, span: self.lower_span(sig.span) },
@@ -776,6 +776,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     i.id,
                     FnDeclKind::Trait,
                     sig.header.coroutine_kind,
+                    attrs,
                 );
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)), false)
             }
@@ -795,6 +796,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     i.id,
                     FnDeclKind::Trait,
                     sig.header.coroutine_kind,
+                    attrs,
                 );
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Provided(body_id)), true)
             }
@@ -911,6 +913,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     i.id,
                     if self.is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent },
                     sig.header.coroutine_kind,
+                    attrs,
                 );
 
                 (generics, hir::ImplItemKind::Fn(sig, body_id))
@@ -1339,8 +1342,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
         id: NodeId,
         kind: FnDeclKind,
         coroutine_kind: Option<CoroutineKind>,
+        attrs: &[hir::Attribute],
     ) -> (&'hir hir::Generics<'hir>, hir::FnSig<'hir>) {
-        let header = self.lower_fn_header(sig.header, hir::Safety::Safe);
+        let header = self.lower_fn_header(sig.header, hir::Safety::Safe, attrs);
         let itctx = ImplTraitContext::Universal;
         let (generics, decl) = self.lower_generics(generics, id, itctx, |this| {
             this.lower_fn_decl(&sig.decl, id, sig.span, kind, coroutine_kind)
@@ -1352,14 +1356,28 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         h: FnHeader,
         default_safety: hir::Safety,
+        attrs: &[hir::Attribute],
     ) -> hir::FnHeader {
         let asyncness = if let Some(CoroutineKind::Async { span, .. }) = h.coroutine_kind {
             hir::IsAsync::Async(span)
         } else {
             hir::IsAsync::NotAsync
         };
+
+        let safety = self.lower_safety(h.safety, default_safety);
+
+        // Treat safe `#[target_feature]` functions as unsafe, but also remember that we did so.
+        let safety = if attrs.iter().any(|attr| attr.has_name(sym::target_feature))
+            && safety.is_safe()
+            && !self.tcx.sess.target.is_like_wasm
+        {
+            hir::HeaderSafety::SafeTargetFeatures
+        } else {
+            safety.into()
+        };
+
         hir::FnHeader {
-            safety: self.lower_safety(h.safety, default_safety),
+            safety,
             asyncness,
             constness: self.lower_constness(h.constness),
             abi: self.lower_extern(h.ext),
diff --git a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
index 37b53bb5bea..1daa17fbaf3 100644
--- a/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
+++ b/compiler/rustc_codegen_ssa/src/codegen_attrs.rs
@@ -250,10 +250,14 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                 }
             }
             sym::target_feature => {
-                if !tcx.is_closure_like(did.to_def_id())
-                    && let Some(fn_sig) = fn_sig()
-                    && fn_sig.skip_binder().safety().is_safe()
-                {
+                let Some(sig) = tcx.hir_node_by_def_id(did).fn_sig() else {
+                    tcx.dcx().span_delayed_bug(attr.span, "target_feature applied to non-fn");
+                    continue;
+                };
+                let safe_target_features =
+                    matches!(sig.header.safety, hir::HeaderSafety::SafeTargetFeatures);
+                codegen_fn_attrs.safe_target_features = safe_target_features;
+                if safe_target_features {
                     if tcx.sess.target.is_like_wasm || tcx.sess.opts.actually_rustdoc {
                         // The `#[target_feature]` attribute is allowed on
                         // WebAssembly targets on all functions, including safe
diff --git a/compiler/rustc_hir/src/hir.rs b/compiler/rustc_hir/src/hir.rs
index dd96b30fefc..740c3ee8c07 100644
--- a/compiler/rustc_hir/src/hir.rs
+++ b/compiler/rustc_hir/src/hir.rs
@@ -3762,9 +3762,30 @@ impl fmt::Display for Constness {
     }
 }
 
+/// The actualy safety specified in syntax. We may treat
+/// its safety different within the type system to create a
+/// "sound by default" system that needs checking this enum
+/// explicitly to allow unsafe operations.
+#[derive(Copy, Clone, Debug, HashStable_Generic, PartialEq, Eq)]
+pub enum HeaderSafety {
+    /// A safe function annotated with `#[target_features]`.
+    /// The type system treats this function as an unsafe function,
+    /// but safety checking will check this enum to treat it as safe
+    /// and allowing calling other safe target feature functions with
+    /// the same features without requiring an additional unsafe block.
+    SafeTargetFeatures,
+    Normal(Safety),
+}
+
+impl From<Safety> for HeaderSafety {
+    fn from(v: Safety) -> Self {
+        Self::Normal(v)
+    }
+}
+
 #[derive(Copy, Clone, Debug, HashStable_Generic)]
 pub struct FnHeader {
-    pub safety: Safety,
+    pub safety: HeaderSafety,
     pub constness: Constness,
     pub asyncness: IsAsync,
     pub abi: ExternAbi,
@@ -3780,7 +3801,18 @@ impl FnHeader {
     }
 
     pub fn is_unsafe(&self) -> bool {
-        self.safety.is_unsafe()
+        self.safety().is_unsafe()
+    }
+
+    pub fn is_safe(&self) -> bool {
+        self.safety().is_safe()
+    }
+
+    pub fn safety(&self) -> Safety {
+        match self.safety {
+            HeaderSafety::SafeTargetFeatures => Safety::Unsafe,
+            HeaderSafety::Normal(safety) => safety,
+        }
     }
 }
 
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index d41b03640b6..86c6532c97d 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -1336,7 +1336,7 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
             {
                 icx.lowerer().lower_fn_ty(
                     hir_id,
-                    sig.header.safety,
+                    sig.header.safety(),
                     sig.header.abi,
                     sig.decl,
                     Some(generics),
@@ -1351,13 +1351,18 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<'_, ty::PolyFn
             kind: TraitItemKind::Fn(FnSig { header, decl, span: _ }, _),
             generics,
             ..
-        }) => {
-            icx.lowerer().lower_fn_ty(hir_id, header.safety, header.abi, decl, Some(generics), None)
-        }
+        }) => icx.lowerer().lower_fn_ty(
+            hir_id,
+            header.safety(),
+            header.abi,
+            decl,
+            Some(generics),
+            None,
+        ),
 
         ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(sig, _, _), .. }) => {
             let abi = tcx.hir().get_foreign_abi(hir_id);
-            compute_sig_of_foreign_fn_decl(tcx, def_id, sig.decl, abi, sig.header.safety)
+            compute_sig_of_foreign_fn_decl(tcx, def_id, sig.decl, abi, sig.header.safety())
         }
 
         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor().is_some() => {
@@ -1405,7 +1410,7 @@ fn lower_fn_sig_recovering_infer_ret_ty<'tcx>(
 
     icx.lowerer().lower_fn_ty(
         icx.tcx().local_def_id_to_hir_id(def_id),
-        sig.header.safety,
+        sig.header.safety(),
         sig.header.abi,
         sig.decl,
         Some(generics),
diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index 39b6823cf0e..3ff6acd79fc 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -2407,7 +2407,7 @@ impl<'a> State<'a> {
         self.print_fn(
             decl,
             hir::FnHeader {
-                safety,
+                safety: safety.into(),
                 abi,
                 constness: hir::Constness::NotConst,
                 asyncness: hir::IsAsync::NotAsync,
@@ -2423,12 +2423,20 @@ impl<'a> State<'a> {
     fn print_fn_header_info(&mut self, header: hir::FnHeader) {
         self.print_constness(header.constness);
 
+        let safety = match header.safety {
+            hir::HeaderSafety::SafeTargetFeatures => {
+                self.word_nbsp("#[target_feature]");
+                hir::Safety::Safe
+            }
+            hir::HeaderSafety::Normal(safety) => safety,
+        };
+
         match header.asyncness {
             hir::IsAsync::NotAsync => {}
             hir::IsAsync::Async(_) => self.word_nbsp("async"),
         }
 
-        self.print_safety(header.safety);
+        self.print_safety(safety);
 
         if header.abi != ExternAbi::Rust {
             self.word_nbsp("extern");
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 9ebc7a4657e..ec7c1efa38e 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -932,10 +932,17 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                         return Err(TypeError::ForceInlineCast);
                     }
 
-                    // Safe `#[target_feature]` functions are not assignable to safe fn pointers
-                    // (RFC 2396).
+                    let fn_attrs = self.tcx.codegen_fn_attrs(def_id);
+                    if matches!(fn_attrs.inline, InlineAttr::Force { .. }) {
+                        return Err(TypeError::ForceInlineCast);
+                    }
+
+                    // FIXME(target_feature): Safe `#[target_feature]` functions could be cast to safe fn pointers (RFC 2396),
+                    // as you can already write that "cast" in user code by wrapping a target_feature fn call in a closure,
+                    // which is safe. This is sound because you already need to be executing code that is satisfying the target
+                    // feature constraints..
                     if b_hdr.safety.is_safe()
-                        && !self.tcx.codegen_fn_attrs(def_id).target_features.is_empty()
+                        && self.tcx.codegen_fn_attrs(def_id).safe_target_features
                     {
                         return Err(TypeError::TargetFeatureCast(def_id));
                     }
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index a406ec9a8fb..cb21961f36b 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -139,7 +139,7 @@ fn typeck_with_fallback<'tcx>(
             // type that has an infer in it, lower the type directly so that it'll
             // be correctly filled with infer. We'll use this inference to provide
             // a suggestion later on.
-            fcx.lowerer().lower_fn_ty(id, header.safety, header.abi, decl, None, None)
+            fcx.lowerer().lower_fn_ty(id, header.safety(), header.abi, decl, None, None)
         } else {
             tcx.fn_sig(def_id).instantiate_identity()
         };
diff --git a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
index 16d868300db..e05f42af6fd 100644
--- a/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
+++ b/compiler/rustc_middle/src/middle/codegen_fn_attrs.rs
@@ -30,6 +30,8 @@ pub struct CodegenFnAttrs {
     /// features (only enabled features are supported right now).
     /// Implied target features have already been applied.
     pub target_features: Vec<TargetFeature>,
+    /// Whether the function was declared safe, but has target features
+    pub safe_target_features: bool,
     /// The `#[linkage = "..."]` attribute on Rust-defined items and the value we found.
     pub linkage: Option<Linkage>,
     /// The `#[linkage = "..."]` attribute on foreign items and the value we found.
@@ -150,6 +152,7 @@ impl CodegenFnAttrs {
             link_name: None,
             link_ordinal: None,
             target_features: vec![],
+            safe_target_features: false,
             linkage: None,
             import_linkage: None,
             link_section: None,
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index bf0ccdc0f10..d2875fb3794 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -222,6 +222,7 @@ pub struct DelegationFnSig {
     pub param_count: usize,
     pub has_self: bool,
     pub c_variadic: bool,
+    pub target_feature: bool,
 }
 
 #[derive(Clone, Copy, Debug)]
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 9fe1caa4b58..ac900edefe1 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -690,7 +690,14 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                 if with_reduced_queries() {
                     p!(print_def_path(def_id, args));
                 } else {
-                    let sig = self.tcx().fn_sig(def_id).instantiate(self.tcx(), args);
+                    let mut sig = self.tcx().fn_sig(def_id).instantiate(self.tcx(), args);
+                    if self.tcx().codegen_fn_attrs(def_id).safe_target_features {
+                        p!("#[target_features] ");
+                        sig = sig.map_bound(|mut sig| {
+                            sig.safety = hir::Safety::Safe;
+                            sig
+                        });
+                    }
                     p!(print(sig), " {{", print_value_path(def_id, args), "}}");
                 }
             }
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index f7071eb139f..6279d0f94af 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -478,19 +478,27 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
                 return; // don't visit the whole expression
             }
             ExprKind::Call { fun, ty: _, args: _, from_hir_call: _, fn_span: _ } => {
-                if self.thir[fun].ty.fn_sig(self.tcx).safety().is_unsafe() {
-                    let func_id = if let ty::FnDef(func_id, _) = self.thir[fun].ty.kind() {
+                let fn_ty = self.thir[fun].ty;
+                let sig = fn_ty.fn_sig(self.tcx);
+                let (callee_features, safe_target_features): (&[_], _) = match fn_ty.kind() {
+                    ty::FnDef(func_id, ..) => {
+                        let cg_attrs = self.tcx.codegen_fn_attrs(func_id);
+                        (&cg_attrs.target_features, cg_attrs.safe_target_features)
+                    }
+                    _ => (&[], false),
+                };
+                if sig.safety().is_unsafe() && !safe_target_features {
+                    let func_id = if let ty::FnDef(func_id, _) = fn_ty.kind() {
                         Some(*func_id)
                     } else {
                         None
                     };
                     self.requires_unsafe(expr.span, CallToUnsafeFunction(func_id));
-                } else if let &ty::FnDef(func_did, _) = self.thir[fun].ty.kind() {
+                } else if let &ty::FnDef(func_did, _) = fn_ty.kind() {
                     // If the called function has target features the calling function hasn't,
                     // the call requires `unsafe`. Don't check this on wasm
                     // targets, though. For more information on wasm see the
                     // is_like_wasm check in hir_analysis/src/collect.rs
-                    let callee_features = &self.tcx.codegen_fn_attrs(func_did).target_features;
                     if !self.tcx.sess.target.options.is_like_wasm
                         && !callee_features.iter().all(|feature| {
                             self.body_target_features.iter().any(|f| f.name == feature.name)
@@ -739,7 +747,10 @@ impl UnsafeOpKind {
     ) {
         let parent_id = tcx.hir().get_parent_item(hir_id);
         let parent_owner = tcx.hir_owner_node(parent_id);
-        let should_suggest = parent_owner.fn_sig().is_some_and(|sig| sig.header.is_unsafe());
+        let should_suggest = parent_owner.fn_sig().is_some_and(|sig| {
+            // Do not suggest for safe target_feature functions
+            matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
+        });
         let unsafe_not_inherited_note = if should_suggest {
             suggest_unsafe_block.then(|| {
                 let body_span = tcx.hir().body(parent_owner.body_id().unwrap()).value.span;
@@ -902,7 +913,7 @@ impl UnsafeOpKind {
             {
                 true
             } else if let Some(sig) = tcx.hir().fn_sig_by_hir_id(*id)
-                && sig.header.is_unsafe()
+                && matches!(sig.header.safety, hir::HeaderSafety::Normal(hir::Safety::Unsafe))
             {
                 true
             } else {
@@ -1111,7 +1122,16 @@ pub(crate) fn check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
 
     let hir_id = tcx.local_def_id_to_hir_id(def);
     let safety_context = tcx.hir().fn_sig_by_hir_id(hir_id).map_or(SafetyContext::Safe, |fn_sig| {
-        if fn_sig.header.safety.is_unsafe() { SafetyContext::UnsafeFn } else { SafetyContext::Safe }
+        match fn_sig.header.safety {
+            // We typeck the body as safe, but otherwise treat it as unsafe everywhere else.
+            // Call sites to other SafeTargetFeatures functions are checked explicitly and don't need
+            // to care about safety of the body.
+            hir::HeaderSafety::SafeTargetFeatures => SafetyContext::Safe,
+            hir::HeaderSafety::Normal(safety) => match safety {
+                hir::Safety::Unsafe => SafetyContext::UnsafeFn,
+                hir::Safety::Safe => SafetyContext::Safe,
+            },
+        }
     });
     let body_target_features = &tcx.body_codegen_attrs(def.to_def_id()).target_features;
     let mut warnings = Vec::new();
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index 7324d3fe786..c4aeaf478bd 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -5019,12 +5019,13 @@ struct ItemInfoCollector<'a, 'ra, 'tcx> {
 }
 
 impl ItemInfoCollector<'_, '_, '_> {
-    fn collect_fn_info(&mut self, sig: &FnSig, id: NodeId) {
+    fn collect_fn_info(&mut self, sig: &FnSig, id: NodeId, attrs: &[Attribute]) {
         let sig = DelegationFnSig {
             header: sig.header,
             param_count: sig.decl.inputs.len(),
             has_self: sig.decl.has_self(),
             c_variadic: sig.decl.c_variadic(),
+            target_feature: attrs.iter().any(|attr| attr.has_name(sym::target_feature)),
         };
         self.r.delegation_fn_sigs.insert(self.r.local_def_id(id), sig);
     }
@@ -5043,7 +5044,7 @@ impl<'ast> Visitor<'ast> for ItemInfoCollector<'_, '_, '_> {
             | ItemKind::Trait(box Trait { ref generics, .. })
             | ItemKind::TraitAlias(ref generics, _) => {
                 if let ItemKind::Fn(box Fn { ref sig, .. }) = &item.kind {
-                    self.collect_fn_info(sig, item.id);
+                    self.collect_fn_info(sig, item.id, &item.attrs);
                 }
 
                 let def_id = self.r.local_def_id(item.id);
@@ -5076,7 +5077,7 @@ impl<'ast> Visitor<'ast> for ItemInfoCollector<'_, '_, '_> {
 
     fn visit_assoc_item(&mut self, item: &'ast AssocItem, ctxt: AssocCtxt) {
         if let AssocItemKind::Fn(box Fn { ref sig, .. }) = &item.kind {
-            self.collect_fn_info(sig, item.id);
+            self.collect_fn_info(sig, item.id, &item.attrs);
         }
         visit::walk_assoc_item(self, item, ctxt);
     }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
index 53300c95fa7..7032f7b9d31 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/mod.rs
@@ -824,9 +824,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     fn cmp_fn_sig(
         &self,
         sig1: &ty::PolyFnSig<'tcx>,
-        fn_def1: Option<(DefId, &'tcx [ty::GenericArg<'tcx>])>,
+        fn_def1: Option<(DefId, Option<&'tcx [ty::GenericArg<'tcx>]>)>,
         sig2: &ty::PolyFnSig<'tcx>,
-        fn_def2: Option<(DefId, &'tcx [ty::GenericArg<'tcx>])>,
+        fn_def2: Option<(DefId, Option<&'tcx [ty::GenericArg<'tcx>]>)>,
     ) -> (DiagStyledString, DiagStyledString) {
         let sig1 = &(self.normalize_fn_sig)(*sig1);
         let sig2 = &(self.normalize_fn_sig)(*sig2);
@@ -850,8 +850,20 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
         // ^^^^^^
-        values.0.push(sig1.safety.prefix_str(), sig1.safety != sig2.safety);
-        values.1.push(sig2.safety.prefix_str(), sig1.safety != sig2.safety);
+        let safety = |fn_def, sig: ty::FnSig<'_>| match fn_def {
+            None => sig.safety.prefix_str(),
+            Some((did, _)) => {
+                if self.tcx.codegen_fn_attrs(did).safe_target_features {
+                    "#[target_features] "
+                } else {
+                    sig.safety.prefix_str()
+                }
+            }
+        };
+        let safety1 = safety(fn_def1, sig1);
+        let safety2 = safety(fn_def2, sig2);
+        values.0.push(safety1, safety1 != safety2);
+        values.1.push(safety2, safety1 != safety2);
 
         // unsafe extern "C" for<'a> fn(&'a T) -> &'a T
         //        ^^^^^^^^^^
@@ -932,23 +944,23 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             (values.1).0.extend(x2.0);
         }
 
-        let fmt = |(did, args)| format!(" {{{}}}", self.tcx.def_path_str_with_args(did, args));
+        let fmt = |did, args| format!(" {{{}}}", self.tcx.def_path_str_with_args(did, args));
 
         match (fn_def1, fn_def2) {
-            (None, None) => {}
-            (Some(fn_def1), Some(fn_def2)) => {
-                let path1 = fmt(fn_def1);
-                let path2 = fmt(fn_def2);
+            (Some((fn_def1, Some(fn_args1))), Some((fn_def2, Some(fn_args2)))) => {
+                let path1 = fmt(fn_def1, fn_args1);
+                let path2 = fmt(fn_def2, fn_args2);
                 let same_path = path1 == path2;
                 values.0.push(path1, !same_path);
                 values.1.push(path2, !same_path);
             }
-            (Some(fn_def1), None) => {
-                values.0.push_highlighted(fmt(fn_def1));
+            (Some((fn_def1, Some(fn_args1))), None) => {
+                values.0.push_highlighted(fmt(fn_def1, fn_args1));
             }
-            (None, Some(fn_def2)) => {
-                values.1.push_highlighted(fmt(fn_def2));
+            (None, Some((fn_def2, Some(fn_args2)))) => {
+                values.1.push_highlighted(fmt(fn_def2, fn_args2));
             }
+            _ => {}
         }
 
         values
@@ -1339,17 +1351,22 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             (ty::FnDef(did1, args1), ty::FnDef(did2, args2)) => {
                 let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
                 let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
-                self.cmp_fn_sig(&sig1, Some((*did1, args1)), &sig2, Some((*did2, args2)))
+                self.cmp_fn_sig(
+                    &sig1,
+                    Some((*did1, Some(args1))),
+                    &sig2,
+                    Some((*did2, Some(args2))),
+                )
             }
 
             (ty::FnDef(did1, args1), ty::FnPtr(sig_tys2, hdr2)) => {
                 let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
-                self.cmp_fn_sig(&sig1, Some((*did1, args1)), &sig_tys2.with(*hdr2), None)
+                self.cmp_fn_sig(&sig1, Some((*did1, Some(args1))), &sig_tys2.with(*hdr2), None)
             }
 
             (ty::FnPtr(sig_tys1, hdr1), ty::FnDef(did2, args2)) => {
                 let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
-                self.cmp_fn_sig(&sig_tys1.with(*hdr1), None, &sig2, Some((*did2, args2)))
+                self.cmp_fn_sig(&sig_tys1.with(*hdr1), None, &sig2, Some((*did2, Some(args2))))
             }
 
             (ty::FnPtr(sig_tys1, hdr1), ty::FnPtr(sig_tys2, hdr2)) => {
@@ -1531,7 +1548,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                         (false, Mismatch::Fixed("existential projection"))
                     }
                 };
-                let Some(vals) = self.values_str(values) else {
+                let Some(vals) = self.values_str(values, cause) else {
                     // Derived error. Cancel the emitter.
                     // NOTE(eddyb) this was `.cancel()`, but `diag`
                     // is borrowed, so we can't fully defuse it.
@@ -1956,7 +1973,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         })
         | ObligationCauseCode::BlockTailExpression(.., source)) = code
             && let hir::MatchSource::TryDesugar(_) = source
-            && let Some((expected_ty, found_ty, _)) = self.values_str(trace.values)
+            && let Some((expected_ty, found_ty, _)) = self.values_str(trace.values, &trace.cause)
         {
             suggestions.push(TypeErrorAdditionalDiags::TryCannotConvert {
                 found: found_ty.content(),
@@ -2085,6 +2102,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
     fn values_str(
         &self,
         values: ValuePairs<'tcx>,
+        cause: &ObligationCause<'tcx>,
     ) -> Option<(DiagStyledString, DiagStyledString, Option<PathBuf>)> {
         match values {
             ValuePairs::Regions(exp_found) => self.expected_found_str(exp_found),
@@ -2109,7 +2127,19 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                 if exp_found.references_error() {
                     return None;
                 }
-                let (exp, fnd) = self.cmp_fn_sig(&exp_found.expected, None, &exp_found.found, None);
+                let (fn_def1, fn_def2) = if let ObligationCauseCode::CompareImplItem {
+                    impl_item_def_id,
+                    trait_item_def_id,
+                    ..
+                } = *cause.code()
+                {
+                    (Some((trait_item_def_id, None)), Some((impl_item_def_id.to_def_id(), None)))
+                } else {
+                    (None, None)
+                };
+
+                let (exp, fnd) =
+                    self.cmp_fn_sig(&exp_found.expected, fn_def1, &exp_found.found, fn_def2);
                 Some((exp, fnd, None))
             }
         }
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
index 2cfccc57c97..1dd09fe7aaf 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/note_and_explain.rs
@@ -461,9 +461,11 @@ impl<T> Trait<T> for X {
                     (ty::FnPtr(_, hdr), ty::FnDef(def_id, _))
                     | (ty::FnDef(def_id, _), ty::FnPtr(_, hdr)) => {
                         if tcx.fn_sig(def_id).skip_binder().safety() < hdr.safety {
-                            diag.note(
+                            if !tcx.codegen_fn_attrs(def_id).safe_target_features {
+                                diag.note(
                                 "unsafe functions cannot be coerced into safe function pointers",
-                            );
+                                );
+                            }
                         }
                     }
                     (ty::Adt(_, _), ty::Adt(def, args))
diff --git a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
index 98b5fb2052f..3acca47025c 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/infer/region.rs
@@ -221,7 +221,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             infer::Subtype(ref trace) => RegionOriginNote::WithRequirement {
                 span: trace.cause.span,
                 requirement: ObligationCauseAsDiagArg(trace.cause.clone()),
-                expected_found: self.values_str(trace.values).map(|(e, f, _)| (e, f)),
+                expected_found: self.values_str(trace.values, &trace.cause).map(|(e, f, _)| (e, f)),
             }
             .add_to_diag(err),
             infer::Reborrow(span) => {
@@ -946,8 +946,10 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         if let infer::Subtype(ref sup_trace) = sup_origin
             && let infer::Subtype(ref sub_trace) = sub_origin
-            && let Some((sup_expected, sup_found, _)) = self.values_str(sup_trace.values)
-            && let Some((sub_expected, sub_found, _)) = self.values_str(sub_trace.values)
+            && let Some((sup_expected, sup_found, _)) =
+                self.values_str(sup_trace.values, &sup_trace.cause)
+            && let Some((sub_expected, sub_found, _)) =
+                self.values_str(sub_trace.values, &sup_trace.cause)
             && sub_expected == sup_expected
             && sub_found == sup_found
         {
diff --git a/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
index 51efe39a7bc..2d248d00066 100644
--- a/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/error_reporting/traits/on_unimplemented.rs
@@ -205,9 +205,15 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
             if self_ty.is_fn() {
                 let fn_sig = self_ty.fn_sig(self.tcx);
-                let shortname = match fn_sig.safety() {
-                    hir::Safety::Safe => "fn",
-                    hir::Safety::Unsafe => "unsafe fn",
+                let shortname = if let ty::FnDef(def_id, _) = self_ty.kind()
+                    && self.tcx.codegen_fn_attrs(def_id).safe_target_features
+                {
+                    "#[target_feature] fn"
+                } else {
+                    match fn_sig.safety() {
+                        hir::Safety::Safe => "fn",
+                        hir::Safety::Unsafe => "unsafe fn",
+                    }
                 };
                 flags.push((sym::_Self, Some(shortname.to_owned())));
             }
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 2ed2df799dd..f619b2c66ac 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -3094,7 +3094,7 @@ fn clean_maybe_renamed_foreign_item<'tcx>(
         let kind = match item.kind {
             hir::ForeignItemKind::Fn(sig, names, generics) => ForeignFunctionItem(
                 clean_function(cx, &sig, generics, FunctionArgs::Names(names)),
-                sig.header.safety,
+                sig.header.safety(),
             ),
             hir::ForeignItemKind::Static(ty, mutability, safety) => ForeignStaticItem(
                 Static { type_: Box::new(clean_ty(ty, cx)), mutability, expr: None },
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index dcee96978d2..ff1c0294fb8 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -668,17 +668,28 @@ impl Item {
                 ty::Asyncness::Yes => hir::IsAsync::Async(DUMMY_SP),
                 ty::Asyncness::No => hir::IsAsync::NotAsync,
             };
-            hir::FnHeader { safety: sig.safety(), abi: sig.abi(), constness, asyncness }
+            hir::FnHeader {
+                safety: if tcx.codegen_fn_attrs(def_id).safe_target_features {
+                    hir::HeaderSafety::SafeTargetFeatures
+                } else {
+                    sig.safety().into()
+                },
+                abi: sig.abi(),
+                constness,
+                asyncness,
+            }
         }
         let header = match self.kind {
             ItemKind::ForeignFunctionItem(_, safety) => {
                 let def_id = self.def_id().unwrap();
                 let abi = tcx.fn_sig(def_id).skip_binder().abi();
                 hir::FnHeader {
-                    safety: if abi == ExternAbi::RustIntrinsic {
-                        intrinsic_operation_unsafety(tcx, def_id.expect_local())
+                    safety: if tcx.codegen_fn_attrs(def_id).safe_target_features {
+                        hir::HeaderSafety::SafeTargetFeatures
+                    } else if abi == ExternAbi::RustIntrinsic {
+                        intrinsic_operation_unsafety(tcx, def_id.expect_local()).into()
                     } else {
-                        safety
+                        safety.into()
                     },
                     abi,
                     constness: if tcx.is_const_fn(def_id) {
diff --git a/src/librustdoc/html/format.rs b/src/librustdoc/html/format.rs
index 621abd53501..92935c72b47 100644
--- a/src/librustdoc/html/format.rs
+++ b/src/librustdoc/html/format.rs
@@ -1637,6 +1637,15 @@ impl PrintWithSpace for hir::Safety {
     }
 }
 
+impl PrintWithSpace for hir::HeaderSafety {
+    fn print_with_space(&self) -> &str {
+        match self {
+            hir::HeaderSafety::SafeTargetFeatures => "",
+            hir::HeaderSafety::Normal(safety) => safety.print_with_space(),
+        }
+    }
+}
+
 impl PrintWithSpace for hir::IsAsync {
     fn print_with_space(&self) -> &str {
         match self {
diff --git a/src/librustdoc/html/render/print_item.rs b/src/librustdoc/html/render/print_item.rs
index e8230e63c0f..1376bdb2e90 100644
--- a/src/librustdoc/html/render/print_item.rs
+++ b/src/librustdoc/html/render/print_item.rs
@@ -469,7 +469,7 @@ fn item_module(w: &mut Buffer, cx: &Context<'_>, item: &clean::Item, items: &[cl
 
                 let unsafety_flag = match myitem.kind {
                     clean::FunctionItem(_) | clean::ForeignFunctionItem(..)
-                        if myitem.fn_header(tcx).unwrap().safety.is_unsafe() =>
+                        if myitem.fn_header(tcx).unwrap().is_unsafe() =>
                     {
                         "<sup title=\"unsafe function\">⚠</sup>"
                     }
diff --git a/src/tools/clippy/clippy_lints/src/derive.rs b/src/tools/clippy/clippy_lints/src/derive.rs
index 7c2f5efd8dd..91ddbb44ff8 100644
--- a/src/tools/clippy/clippy_lints/src/derive.rs
+++ b/src/tools/clippy/clippy_lints/src/derive.rs
@@ -419,7 +419,7 @@ impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
         id: LocalDefId,
     ) -> Self::Result {
         if let Some(header) = kind.header()
-            && header.safety.is_unsafe()
+            && header.is_unsafe()
         {
             ControlFlow::Break(())
         } else {
diff --git a/src/tools/clippy/clippy_lints/src/doc/missing_headers.rs b/src/tools/clippy/clippy_lints/src/doc/missing_headers.rs
index 3e2b7055de4..8e2af6bf14a 100644
--- a/src/tools/clippy/clippy_lints/src/doc/missing_headers.rs
+++ b/src/tools/clippy/clippy_lints/src/doc/missing_headers.rs
@@ -32,7 +32,7 @@ pub fn check(
     }
 
     let span = cx.tcx.def_span(owner_id);
-    match (headers.safety, sig.header.safety) {
+    match (headers.safety, sig.header.safety()) {
         (false, Safety::Unsafe) => span_lint(
             cx,
             MISSING_SAFETY_DOC,
diff --git a/src/tools/clippy/clippy_lints/src/functions/misnamed_getters.rs b/src/tools/clippy/clippy_lints/src/functions/misnamed_getters.rs
index 017571c38db..854fe144c29 100644
--- a/src/tools/clippy/clippy_lints/src/functions/misnamed_getters.rs
+++ b/src/tools/clippy/clippy_lints/src/functions/misnamed_getters.rs
@@ -34,7 +34,7 @@ pub fn check_fn(cx: &LateContext<'_>, kind: FnKind<'_>, decl: &FnDecl<'_>, body:
         ImplicitSelfKind::None => return,
     };
 
-    let name = if sig.header.safety.is_unsafe() {
+    let name = if sig.header.is_unsafe() {
         name.strip_suffix("_unchecked").unwrap_or(name)
     } else {
         name
diff --git a/src/tools/clippy/clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs b/src/tools/clippy/clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs
index 3ded8dc3012..8a74951ef63 100644
--- a/src/tools/clippy/clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs
+++ b/src/tools/clippy/clippy_lints/src/functions/not_unsafe_ptr_arg_deref.rs
@@ -20,8 +20,8 @@ pub(super) fn check_fn<'tcx>(
     def_id: LocalDefId,
 ) {
     let safety = match kind {
-        intravisit::FnKind::ItemFn(_, _, hir::FnHeader { safety, .. }) => safety,
-        intravisit::FnKind::Method(_, sig) => sig.header.safety,
+        intravisit::FnKind::ItemFn(_, _, header) => header.safety(),
+        intravisit::FnKind::Method(_, sig) => sig.header.safety(),
         intravisit::FnKind::Closure => return,
     };
 
@@ -31,7 +31,7 @@ pub(super) fn check_fn<'tcx>(
 pub(super) fn check_trait_item<'tcx>(cx: &LateContext<'tcx>, item: &'tcx hir::TraitItem<'_>) {
     if let hir::TraitItemKind::Fn(ref sig, hir::TraitFn::Provided(eid)) = item.kind {
         let body = cx.tcx.hir().body(eid);
-        check_raw_ptr(cx, sig.header.safety, sig.decl, body, item.owner_id.def_id);
+        check_raw_ptr(cx, sig.header.safety(), sig.decl, body, item.owner_id.def_id);
     }
 }
 
diff --git a/src/tools/clippy/clippy_lints/src/inherent_to_string.rs b/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
index e096dd25175..415b47adac5 100644
--- a/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
+++ b/src/tools/clippy/clippy_lints/src/inherent_to_string.rs
@@ -95,7 +95,7 @@ impl<'tcx> LateLintPass<'tcx> for InherentToString {
         if let ImplItemKind::Fn(ref signature, _) = impl_item.kind
             // #11201
             && let header = signature.header
-            && header.safety.is_safe()
+            && header.is_safe()
             && header.abi == Abi::Rust
             && impl_item.ident.name == sym::to_string
             && let decl = signature.decl
diff --git a/src/tools/clippy/clippy_lints/src/methods/mod.rs b/src/tools/clippy/clippy_lints/src/methods/mod.rs
index 51351f6b7cd..3965c4d4087 100644
--- a/src/tools/clippy/clippy_lints/src/methods/mod.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/mod.rs
@@ -5309,7 +5309,7 @@ fn lint_binary_expr_with_method_call(cx: &LateContext<'_>, info: &mut BinaryExpr
 }
 
 const FN_HEADER: hir::FnHeader = hir::FnHeader {
-    safety: hir::Safety::Safe,
+    safety: hir::HeaderSafety::Normal(hir::Safety::Safe),
     constness: hir::Constness::NotConst,
     asyncness: hir::IsAsync::NotAsync,
     abi: rustc_target::spec::abi::Abi::Rust,
diff --git a/src/tools/clippy/clippy_lints/src/new_without_default.rs b/src/tools/clippy/clippy_lints/src/new_without_default.rs
index abdce69e764..688374b5676 100644
--- a/src/tools/clippy/clippy_lints/src/new_without_default.rs
+++ b/src/tools/clippy/clippy_lints/src/new_without_default.rs
@@ -75,7 +75,7 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
                     if let hir::ImplItemKind::Fn(ref sig, _) = impl_item.kind {
                         let name = impl_item.ident.name;
                         let id = impl_item.owner_id;
-                        if sig.header.safety.is_unsafe() {
+                        if sig.header.is_unsafe() {
                             // can't be implemented for unsafe new
                             return;
                         }
diff --git a/src/tools/clippy/clippy_lints/src/ptr.rs b/src/tools/clippy/clippy_lints/src/ptr.rs
index a86926d8416..506adf0f2cc 100644
--- a/src/tools/clippy/clippy_lints/src/ptr.rs
+++ b/src/tools/clippy/clippy_lints/src/ptr.rs
@@ -541,7 +541,7 @@ fn check_mut_from_ref<'tcx>(cx: &LateContext<'tcx>, sig: &FnSig<'_>, body: Optio
             .collect();
         if let Some(args) = args
             && !args.is_empty()
-            && body.is_none_or(|body| sig.header.safety.is_unsafe() || contains_unsafe_block(cx, body.value))
+            && body.is_none_or(|body| sig.header.is_unsafe() || contains_unsafe_block(cx, body.value))
         {
             span_lint_and_then(
                 cx,
diff --git a/tests/ui/async-await/async-closures/fn-exception-target-features.stderr b/tests/ui/async-await/async-closures/fn-exception-target-features.stderr
index db5895108bb..37977b45250 100644
--- a/tests/ui/async-await/async-closures/fn-exception-target-features.stderr
+++ b/tests/ui/async-await/async-closures/fn-exception-target-features.stderr
@@ -1,11 +1,12 @@
-error[E0277]: the trait bound `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}: AsyncFn()` is not satisfied
+error[E0277]: the trait bound `#[target_features] fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}: AsyncFn()` is not satisfied
   --> $DIR/fn-exception-target-features.rs:16:10
    |
 LL |     test(target_feature);
-   |     ---- ^^^^^^^^^^^^^^ the trait `AsyncFn()` is not implemented for fn item `fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}`
+   |     ---- ^^^^^^^^^^^^^^ unsatisfied trait bound
    |     |
    |     required by a bound introduced by this call
    |
+   = help: the trait `AsyncFn()` is not implemented for fn item `#[target_features] fn() -> Pin<Box<(dyn Future<Output = ()> + 'static)>> {target_feature}`
 note: required by a bound in `test`
   --> $DIR/fn-exception-target-features.rs:13:17
    |
diff --git a/tests/ui/macros/issue-68060.rs b/tests/ui/macros/issue-68060.rs
index 1a826bd60e0..4eddb96848c 100644
--- a/tests/ui/macros/issue-68060.rs
+++ b/tests/ui/macros/issue-68060.rs
@@ -3,8 +3,6 @@ fn main() {
         .map(
             #[target_feature(enable = "")]
             //~^ ERROR: attribute should be applied to a function
-            //~| ERROR: feature named `` is not valid
-            //~| NOTE: `` is not valid for this target
             #[track_caller]
             //~^ ERROR: `#[track_caller]` on closures is currently unstable
             //~| NOTE: see issue #87417
diff --git a/tests/ui/macros/issue-68060.stderr b/tests/ui/macros/issue-68060.stderr
index 5724a9ea438..ef2246d5bd6 100644
--- a/tests/ui/macros/issue-68060.stderr
+++ b/tests/ui/macros/issue-68060.stderr
@@ -7,14 +7,8 @@ LL |             #[target_feature(enable = "")]
 LL |             |_| (),
    |             ------ not a function definition
 
-error: the feature named `` is not valid for this target
-  --> $DIR/issue-68060.rs:4:30
-   |
-LL |             #[target_feature(enable = "")]
-   |                              ^^^^^^^^^^^ `` is not valid for this target
-
 error[E0658]: `#[track_caller]` on closures is currently unstable
-  --> $DIR/issue-68060.rs:8:13
+  --> $DIR/issue-68060.rs:6:13
    |
 LL |             #[track_caller]
    |             ^^^^^^^^^^^^^^^
@@ -23,6 +17,6 @@ LL |             #[track_caller]
    = help: add `#![feature(closure_track_caller)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0658`.
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-ptr.stderr b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-ptr.stderr
index cc941be5479..a2bda229d10 100644
--- a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-ptr.stderr
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-ptr.stderr
@@ -10,13 +10,8 @@ LL |     let foo: fn() = foo;
    |              expected due to this
    |
    = note: expected fn pointer `fn()`
-                 found fn item `fn() {foo}`
-   = note: fn items are distinct from fn pointers
+                 found fn item `#[target_features] fn() {foo}`
    = note: functions with `#[target_feature]` can only be coerced to `unsafe` function pointers
-help: consider casting to a fn pointer
-   |
-LL |     let foo: fn() = foo as fn();
-   |                     ~~~~~~~~~~~
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
index 3c370a1b8f3..3eae79faf42 100644
--- a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.rs
@@ -21,9 +21,9 @@ fn call_once(f: impl FnOnce()) {
 }
 
 fn main() {
-    call(foo); //~ ERROR expected a `Fn()` closure, found `fn() {foo}`
-    call_mut(foo); //~ ERROR expected a `FnMut()` closure, found `fn() {foo}`
-    call_once(foo); //~ ERROR expected a `FnOnce()` closure, found `fn() {foo}`
+    call(foo); //~ ERROR expected a `Fn()` closure, found `#[target_features] fn() {foo}`
+    call_mut(foo); //~ ERROR expected a `FnMut()` closure, found `#[target_features] fn() {foo}`
+    call_once(foo); //~ ERROR expected a `FnOnce()` closure, found `#[target_features] fn() {foo}`
 
     call(foo_unsafe);
     //~^ ERROR expected a `Fn()` closure, found `unsafe fn() {foo_unsafe}`
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
index 4c07f4d6b99..2915b9ad1b3 100644
--- a/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/fn-traits.stderr
@@ -1,13 +1,13 @@
-error[E0277]: expected a `Fn()` closure, found `fn() {foo}`
+error[E0277]: expected a `Fn()` closure, found `#[target_features] fn() {foo}`
   --> $DIR/fn-traits.rs:24:10
    |
 LL |     call(foo);
-   |     ---- ^^^ expected an `Fn()` closure, found `fn() {foo}`
+   |     ---- ^^^ expected an `Fn()` closure, found `#[target_features] fn() {foo}`
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `Fn()` is not implemented for fn item `fn() {foo}`
-   = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
+   = help: the trait `Fn()` is not implemented for fn item `#[target_features] fn() {foo}`
+   = note: wrap the `#[target_features] fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
    = note: `#[target_feature]` functions do not implement the `Fn` traits
 note: required by a bound in `call`
   --> $DIR/fn-traits.rs:11:17
@@ -15,16 +15,16 @@ note: required by a bound in `call`
 LL | fn call(f: impl Fn()) {
    |                 ^^^^ required by this bound in `call`
 
-error[E0277]: expected a `FnMut()` closure, found `fn() {foo}`
+error[E0277]: expected a `FnMut()` closure, found `#[target_features] fn() {foo}`
   --> $DIR/fn-traits.rs:25:14
    |
 LL |     call_mut(foo);
-   |     -------- ^^^ expected an `FnMut()` closure, found `fn() {foo}`
+   |     -------- ^^^ expected an `FnMut()` closure, found `#[target_features] fn() {foo}`
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `FnMut()` is not implemented for fn item `fn() {foo}`
-   = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
+   = help: the trait `FnMut()` is not implemented for fn item `#[target_features] fn() {foo}`
+   = note: wrap the `#[target_features] fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
    = note: `#[target_feature]` functions do not implement the `Fn` traits
 note: required by a bound in `call_mut`
   --> $DIR/fn-traits.rs:15:25
@@ -32,16 +32,16 @@ note: required by a bound in `call_mut`
 LL | fn call_mut(mut f: impl FnMut()) {
    |                         ^^^^^^^ required by this bound in `call_mut`
 
-error[E0277]: expected a `FnOnce()` closure, found `fn() {foo}`
+error[E0277]: expected a `FnOnce()` closure, found `#[target_features] fn() {foo}`
   --> $DIR/fn-traits.rs:26:15
    |
 LL |     call_once(foo);
-   |     --------- ^^^ expected an `FnOnce()` closure, found `fn() {foo}`
+   |     --------- ^^^ expected an `FnOnce()` closure, found `#[target_features] fn() {foo}`
    |     |
    |     required by a bound introduced by this call
    |
-   = help: the trait `FnOnce()` is not implemented for fn item `fn() {foo}`
-   = note: wrap the `fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
+   = help: the trait `FnOnce()` is not implemented for fn item `#[target_features] fn() {foo}`
+   = note: wrap the `#[target_features] fn() {foo}` in a closure with no arguments: `|| { /* code */ }`
    = note: `#[target_feature]` functions do not implement the `Fn` traits
 note: required by a bound in `call_once`
   --> $DIR/fn-traits.rs:19:22
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.rs b/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.rs
index df575b0f6b6..a2ac6ff45fc 100644
--- a/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.rs
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.rs
@@ -13,6 +13,7 @@ impl Foo for Bar {
     #[target_feature(enable = "sse2")]
     //~^ ERROR cannot be applied to safe trait method
     fn foo(&self) {}
+    //~^ ERROR method `foo` has an incompatible type for trait
 
     #[target_feature(enable = "sse2")]
     unsafe fn unsf_foo(&self) {}
diff --git a/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.stderr b/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.stderr
index 00efbb52f15..1ab1fad64cc 100644
--- a/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.stderr
+++ b/tests/ui/rfcs/rfc-2396-target_feature-11/trait-impl.stderr
@@ -7,8 +7,22 @@ LL |
 LL |     fn foo(&self) {}
    |     ------------- not an `unsafe` function
 
+error[E0053]: method `foo` has an incompatible type for trait
+  --> $DIR/trait-impl.rs:15:5
+   |
+LL |     fn foo(&self) {}
+   |     ^^^^^^^^^^^^^ expected safe fn, found unsafe fn
+   |
+note: type in trait
+  --> $DIR/trait-impl.rs:6:5
+   |
+LL |     fn foo(&self);
+   |     ^^^^^^^^^^^^^^
+   = note: expected signature `fn(&Bar)`
+              found signature `#[target_features] fn(&Bar)`
+
 error: `#[target_feature(..)]` cannot be applied to safe trait method
-  --> $DIR/trait-impl.rs:22:5
+  --> $DIR/trait-impl.rs:23:5
    |
 LL |     #[target_feature(enable = "sse2")]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot be applied to safe trait method
@@ -16,5 +30,6 @@ LL |
 LL |     fn foo(&self) {}
    |     ------------- not an `unsafe` function
 
-error: aborting due to 2 previous errors
+error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0053`.
diff --git a/tests/ui/target-feature/invalid-attribute.rs b/tests/ui/target-feature/invalid-attribute.rs
index 2f951c4a00a..c0f5b6b2fb2 100644
--- a/tests/ui/target-feature/invalid-attribute.rs
+++ b/tests/ui/target-feature/invalid-attribute.rs
@@ -97,6 +97,7 @@ impl Foo {}
 
 trait Quux {
     fn foo(); //~ NOTE `foo` from trait
+    //~^ NOTE: type in trait
 }
 
 impl Quux for Foo {
@@ -106,6 +107,9 @@ impl Quux for Foo {
     //~| NOTE: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
     fn foo() {}
     //~^ NOTE not an `unsafe` function
+    //~| ERROR: incompatible type for trait
+    //~| NOTE: expected safe fn, found unsafe fn
+    //~| NOTE: expected signature `fn()`
 }
 
 fn main() {
diff --git a/tests/ui/target-feature/invalid-attribute.stderr b/tests/ui/target-feature/invalid-attribute.stderr
index bf48911edec..10fcf65bb9a 100644
--- a/tests/ui/target-feature/invalid-attribute.stderr
+++ b/tests/ui/target-feature/invalid-attribute.stderr
@@ -126,7 +126,7 @@ LL | impl Foo {}
    | ----------- not a function definition
 
 error: attribute should be applied to a function definition
-  --> $DIR/invalid-attribute.rs:112:5
+  --> $DIR/invalid-attribute.rs:116:5
    |
 LL |       #[target_feature(enable = "sse2")]
    |       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -138,7 +138,7 @@ LL | |     }
    | |_____- not a function definition
 
 error: attribute should be applied to a function definition
-  --> $DIR/invalid-attribute.rs:120:5
+  --> $DIR/invalid-attribute.rs:124:5
    |
 LL |     #[target_feature(enable = "sse2")]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -193,7 +193,7 @@ LL |     fn foo();
    |     --------- `foo` from trait
 
 error[E0658]: `#[target_feature(..)]` can only be applied to `unsafe` functions
-  --> $DIR/invalid-attribute.rs:103:5
+  --> $DIR/invalid-attribute.rs:104:5
    |
 LL |     #[target_feature(enable = "sse2")]
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -205,7 +205,21 @@ LL |     fn foo() {}
    = help: add `#![feature(target_feature_11)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
-error: aborting due to 23 previous errors
+error[E0053]: method `foo` has an incompatible type for trait
+  --> $DIR/invalid-attribute.rs:108:5
+   |
+LL |     fn foo() {}
+   |     ^^^^^^^^ expected safe fn, found unsafe fn
+   |
+note: type in trait
+  --> $DIR/invalid-attribute.rs:99:5
+   |
+LL |     fn foo();
+   |     ^^^^^^^^^
+   = note: expected signature `fn()`
+              found signature `#[target_features] fn()`
+
+error: aborting due to 24 previous errors
 
-Some errors have detailed explanations: E0046, E0658.
+Some errors have detailed explanations: E0046, E0053, E0658.
 For more information about an error, try `rustc --explain E0046`.